With the advent of electronic keyboards on terminals and typewriters, there has been a need for improving the operation of those keyboards to accomplish repeat characters. On mechanical keyboards which have the typamatic or repeat character capability, by holding the keybutton depressed to a second force level, the machine will repeatedly cycle and print repetitively the character indicated by the keybutton.
However, with keyboards using electrical or electronic contacts or a change in capacitance to indicate the depression of a keybutton for character selection, it is preferable to utilize an alternate technique of selecting repeated characters from the second depression force level approach.
With electronic keyboards, whether they be capacitance or switch arrangements, all the positions on the keyboard are scanned or sequentially queried to determine whether a keybutton has been depressed to select the character. One technique for repeating a character is the depression and release and redepression of the desired key. This approach will produce a plurality of identically repeated characters.
For keyboards having the repeat character characteristic, the keybutton may be held depressed and the processor which controls the scanning and other organizational functions of the keyboard, will detect the held-down condition and repeat the character automatically. This approach, although having many advantages, requires a timed delay after the depression of the keybutton before a second and subsequent cycles are initiated to insure that the typist has had an opportunity to remove the finger from the button and thereby not inadvertently initiate detection of the made or depressed condition indicating repetitive characters. This may be accomplished by requiring a timed delay of 500 or 600 milliseconds from the time that the first keybutton closing is sensed. If, after the predetermined delay time, the key is determined to be still held in a depressed condition, the processor assumes that repetitive characters are to be printed and initiates the appropriate printing cycles to form those characters on the record media, typically at machine cycle speed and continuing until such time as the keybutton is released and the keyboard processor detects the change of condition from a depressed key to a released key.
Typewriters and data processing terminals utilizing electronic keyboards and which are presently in the market utilize a fixed time delay, typically 600 milliseconds. This 600 millisecond delay is too long a period for a fast typist since a fast typist can typically key characters at an average rate of one character every 200 milliseconds or less. The net result of the 600 millisecond delay period is that a fast typist has their typing rhythm interrupted by virtue of having to stop and wait an additional 300-400 milliseconds for the repeat mode to begin to be initiated.
A shorter time delay is undesirable from the standpoint that a slow or sluggish typist will allow the fingers to rest on the keyboard keys and may inadvertently leave the key depressed for such a period of time as is necessary to initiate the repetitive printing or typamatic printing of a character.
Inasmuch as the operator or typist is unique in their timing, rhythm, speed and the length of time that a key is held depressed, it is not possible to provide a single timed delay which is acceptable or optimal for a great majority of the operators.